If it hasn't happened to you already, you probably know someone who has experienced a not-so-happy dog during a run or a bike ride. Even if you are a dog lover or own a dog, running into one that is unknown or angry can be scary. To some runners and cyclists, this may be easily brushed off. It's just a part of exercising outside! But for others (like us!) it is downright terrifying. There is nothing more frightening than hearing that low growl, instantly triggering your fight or flight system. There are around 4.5 million dog bites in the US every year. There isn't a lot of solid data on how many of those were runners or cyclists, but odds are that you may eventually run into this scenario.

What should I do?

• Stay calm. Easier said than done, right? But dogs can sense how you're feeling.

• Check out the animal's behavior. The following are signs of aggression:

• Slow down, walk or even stop. The faster you're running, the more you look like something to chase. The only exception to this would be if you saw an opportunity for shelter and you felt that you could make it there safely.

• Create some distance between you and the dog. Especially if it seems to be protective of its "territory".

• If you're wearing a hat or sunglasses, think about taking them off. They can be a trigger for some dogs.

If you're on your bike...

• Dogs are more likely to see you as something to chase if you're going fast. That being said, if you feel confident you can outsprint one...go for it. If you have some distance on this hypothetical animal, it would be better for everyone for you to leave the situation.

• But if you're not 100% confident you can outsprint the dog, don't try. Once the dog has started chasing you, it will be more difficult to distract it. No matter if you started on two wheels or on foot if you end up face to face with an aggressive dog the following could prevent the worst case scenario.

• Your voice: deep and confident, use your best "pack leader" tone. Tell it to "Go home!" or "No! Get!"

• A "dog horn" or whistle: A loud noise can startle the animal and get it off your heels. A whistle could be kept around your neck, while a horn could be mounted on the handlebars of your bike.

• Pepper spray: Some people don't agree with the use of pepper spray on a dog. But if you're carrying it for protection against other types of predators and find yourself in this situation, it will do the trick.

• Taser: If you carry one, we're assuming you know to only use it when you have to! Some dogs are also afraid of the sound it makes.

• Citronella spray: A better alternative if you don't like the idea of using pepper spray. We found one recipe here.

Okay, worst has come to worst and this dog won't back down. If you have tried everything and you are physically being attacked, play dead. Roll into a ball and cover your head and neck with your hands. Curl your fingers into fists to protect them.

While we certainly hope you never encounter this situation, it is important to be prepared. The absolute best way to avoid an unfriendly dog is knowing your route. We can all agree that avoiding an attack in the first place is preferable.

If you are bitten by a dog, the Humane Society says to:

• Immediately wash the wound thoroughly with soap and warm water.

• Contact your physician for additional care and advice.

• Report the bite to your local animal care and control agency.

Have you ever had a run-in with an aggressive dog? What happened? Tell us about it in the comments!